Water form or Barback rollers are used in the printing industry to spread water over a printing plate as evenly and as thinly as possible to enable the printing plate to produce a better printed image. When water and/or other liquids are distributed over the printing plate, it covers those areas of the plate that bear printing images to which ink is applied for printing as well as those areas that are free or devoid of printing images and are intended to be free of print. If the water or other liquid is applied and spread too thickly or too unevenly, printing is adversely affected and the printed image that is produced is often unacceptable.
The present roller provides a roller surface that is comprised of two rubber or rubber-like compounds of different durometers. The compounds are interwoven at the roller surface in a helical direction to cause the liquid to flow in a lateral direction over the surface of the printing plate, thereby assuring that the whole of the printing plate is covered by the liquid. During such forced flow of liquid the portion of the roller surface that is of softer durometer tends to yield under the pressure of the liquid thereagainst and forms a duct along which the liquid is helically conducted and deposited on the surface of the printing plate. At the same time, the helical portion of the roller surface that is of harder durometer and is less yielding engages and presses against the surface of the printing plate and wipes the deposited liquid so as to spread it evenly and thinly over the printing plate surface.
Obviously, the durometer of one of the interwoven compounds may be selected to be more or less yieldable to provide for the conduct of more or less of the liquid to the printing plate surface as is desired. Similarly, the hardness and less yieldability of the wiping or spreading one of the compounds may be selected to provide greater rigidity of a desired stiffness for wiping engagement with the printing plate. If the ductor or conductor compound is more yieldable, it will conduct more liquid to the printing plate. If the wiping compound is selected to be of a harder durometer, it may wipe and spread the deposited liquid thinner against the surface of the printing plate.
Rollers having helices have been taught before and are exemplified in the U.S. Pat. Nos. 828,241 to Peterson, 945,411 to Peterson, 1,079,339 to Hennessey, 1,547,060 to May, 2,689,522 to Curtis, 2,690,119 to Black, 2,996,981 to Reinartz et al, and 3,651,758 to Harrod. None of the aforementioned prior art patents have recognized or taught the use or the construction of a monolithic roller having a plurality of surfaces that are formed of different materials, each of which has a different durometer for the purpose of alternately conducting and wiping a liquid on the surface of a printing plate or other surface, nor have any of them taught the method of making such a roller.
The above description, as well as further objects, features, and advantages of the present invention, will be more fully appreciated by reference to the following detailed description of a presently preferred, but nonetheless illustrative, embodiment in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein: